Pharmacology: Antiviral Drugs Practice Exam

EXPLANATION

✔Correct answer:

Protease. Protease is the enzyme crucial for the maturation of infectious viruses, particularly in the context of HIV (Human Immunodeficiency Virus). In the viral lifecycle, protease plays a vital role in processing the viral polyproteins into functional viral proteins. After the viral RNA is transcribed and translated into long chains of polyproteins, protease cleaves these polyproteins into smaller, functional units that are essential for the assembly of mature viral particles. Without protease, these polyproteins would remain unprocessed, and the virus would not be able to assemble properly or become infectious.

Protease is integral to the lifecycle of many viruses, including HIV. After a virus infects a host cell, its genetic material is replicated, and viral proteins are synthesized as large precursor polyproteins. The protease enzyme cleaves these polyproteins at specific sites to produce the individual proteins needed to form a mature, infectious virus. Inhibiting protease prevents the virus from maturing, rendering it non-infectious.

Imagine you're baking a cake (representing the virus), and you have all the ingredients mixed together in one large batter (the polyprotein). Protease acts like a knife that slices the cake into individual pieces, each representing a functional part of the virus. Without the knife (protease), the cake can't be properly divided, and the pieces (viral proteins) can't be used to build the finished product (a mature virus).

In clinical practice, protease inhibitors (PIs) are a class of antiviral drugs used to treat infections such as HIV by inhibiting the protease enzyme. This prevents the maturation of the virus, reducing its ability to infect new cells. Nurses should be aware of potential side effects of protease inhibitors, such as metabolic changes, and educate patients on adherence to their medication regimen to prevent resistance.

• Educate patients on the importance of strict adherence to protease inhibitors to prevent HIV resistance.
• Monitor for metabolic side effects, including hyperlipidemia and insulin resistance, in patients taking protease inhibitors.
• Ensure that patients are aware of possible drug interactions with protease inhibitors.

✘Incorrect answer options:

Reverse transcriptase Reverse transcriptase is an enzyme used by retroviruses like HIV to convert their RNA into DNA, allowing them to integrate into the host cell's genome. While crucial in the early stages of the viral lifecycle, it is not directly involved in the maturation of infectious viral particles.

Nucleosidase Nucleosidase is not a relevant enzyme in the context of viral maturation. It refers to enzymes involved in nucleotide metabolism, not viral protein processing or maturation.

CCR5-ase CCR5-ase does not exist as an enzyme. CCR5 is a co-receptor used by HIV to enter host cells, and drugs that block CCR5 (like maraviroc) are used to prevent viral entry, but CCR5 itself is not an enzyme involved in viral maturation.

EXPLANATION

✔Correct answer:

CBC with differential count. CBC with differential count is the key parameter to monitor in patients receiving both cyclosporine and zidovudine. Cyclosporine is an immunosuppressant used primarily in organ transplantation to prevent rejection, and zidovudine is an antiretroviral medication used in the treatment of HIV. Both of these drugs can have significant hematological side effects, making it essential to monitor the complete blood count (CBC) with differential.

• Cyclosporine can lead to bone marrow suppression, resulting in leukopenia (low white blood cell count) and thrombocytopenia (low platelet count).
• Zidovudine is well known for causing anemia and neutropenia (a reduction in neutrophils, which are a type of white blood cell). Monitoring the CBC with differential will help in early detection of these conditions, allowing for timely interventions to prevent complications such as infections, anemia, or bleeding.

Both drugs can impact the bone marrow's ability to produce blood cells. Cyclosporine can suppress the immune system to prevent organ rejection, but this suppression can also reduce the production of essential blood cells. Zidovudine’s effect on bone marrow suppression can further compound this, leading to significant risks if not monitored appropriately.

Think of the bone marrow as a factory that produces essential products (blood cells). Cyclosporine and zidovudine can slow down this factory, leading to a shortage of products. Monitoring the CBC is like checking the factory's output to ensure it's still meeting demand.

Nurses should routinely monitor the CBC with differential in patients on these medications and be vigilant for signs of bone marrow suppression, such as increased susceptibility to infections (due to low white blood cells), fatigue (due to anemia), and easy bruising or bleeding (due to low platelets).

• Monitor for signs and symptoms of infection, such as fever and sore throat, which could indicate neutropenia.
• Assess for signs of anemia, including fatigue, pallor, and shortness of breath.
• Watch for any unusual bruising or bleeding, which could suggest thrombocytopenia.
• Collaborate with the healthcare provider to adjust dosages or provide supportive therapies like blood transfusions if necessary.

✘Incorrect answer options:

Skin lesions, temperature, and color. While monitoring skin lesions, temperature, and color can be relevant in certain conditions (e.g., infections, drug reactions), they are not the most critical parameters to monitor for patients receiving cyclosporine and zidovudine. The primary concern is hematological side effects, which are best assessed through CBC.

Flu-like symptoms. Flu-like symptoms could suggest an adverse reaction or an infection, which is possible in immunocompromised patients. However, they are nonspecific and do not directly monitor the key hematologic risks associated with these drugs.

Level of consciousness. Altered level of consciousness can be a sign of severe adverse effects or complications, such as infection-related sepsis, but it is not the primary focus when monitoring the combined use of cyclosporine and zidovudine. It is more crucial to monitor the CBC to prevent such severe complications from occurring.

EXPLANATION

✔Correct answer:

Oseltamivir. Oseltamivir (commonly known by the brand name Tamiflu) is an antiviral medication specifically effective against influenza viruses, including H1N1. It is a neuraminidase inhibitor, which means it blocks the function of the viral neuraminidase enzyme. This enzyme is crucial for the release of new viral particles from infected cells. By inhibiting this enzyme, oseltamivir reduces the spread of the virus within the body, shortens the duration of illness, and helps to alleviate symptoms. It is most effective when administered within 48 hours of symptom onset.

H1N1 influenza is a type of viral infection caused by the influenza A virus. The virus infects the respiratory tract, leading to symptoms such as fever, cough, sore throat, body aches, and fatigue. Neuraminidase inhibitors like oseltamivir are important in the treatment and prophylaxis of influenza as they interfere with the replication of the virus, thus limiting its ability to infect additional cells.

Think of the influenza virus as a band of thieves trying to escape a building (the infected cell) after robbing it. Oseltamivir acts like a security system that locks the doors, preventing the thieves from escaping and causing more damage elsewhere (infecting other cells).

Nurses should ensure that oseltamivir is administered as soon as possible after the onset of influenza symptoms for optimal effectiveness. Additionally, patients should be educated on the importance of completing the full course of the medication to prevent resistance.

• Monitor for potential side effects, such as nausea, vomiting, and headache.
• Educate the patient on the importance of early treatment initiation for better outcomes.
• Ensure the patient is aware of the need for supportive care, including hydration and rest.
• Encourage the patient to receive an annual flu vaccine as preventive care.

✘Incorrect answer options:

Zidovudine Zidovudine is an antiretroviral medication used to treat HIV, not influenza. It works by inhibiting the reverse transcriptase enzyme, which is necessary for the replication of HIV, not the influenza virus. Therefore, it is not effective against H1N1 or other influenza viruses.

Acyclovir Acyclovir is an antiviral medication primarily used to treat infections caused by herpes viruses, such as herpes simplex virus (HSV) and varicella-zoster virus (VZV). It works by inhibiting viral DNA synthesis, but it is not effective against the influenza virus, including H1N1.

Selzentry Selzentry (maraviroc) is another antiretroviral medication used in the treatment of HIV. It works by blocking the CCR5 co-receptor on T-cells, preventing HIV from entering and infecting the cells. Like zidovudine, it is not effective against the influenza virus.

EXPLANATION

✔Correct answer:

Amantadine (Symmetrel) Amantadine is an antiviral medication that is commonly used to treat or prevent respiratory infections caused by the influenza A virus. It works by interfering with the viral replication process, thus reducing the severity of the infection. Given that the patient is diagnosed with a severe case of respiratory flu, which is often caused by the influenza virus, Amantadine is the most appropriate medication among the choices provided. It is particularly useful when administered within the first 48 hours of symptom onset.

Influenza viruses, particularly influenza A, cause respiratory infections by invading and replicating within the respiratory tract epithelial cells. Amantadine blocks the M2 protein on the virus's surface, which is necessary for the uncoating and release of the viral RNA into host cells. By inhibiting this process, Amantadine reduces viral replication and shortens the duration of symptoms.

Think of the influenza virus as a key that needs to enter a lock (the host cell) to cause infection. Amantadine works like glue that jams the keyhole, preventing the key (virus) from unlocking and entering the cell to cause damage.

When administering Amantadine, it is important for nurses to:

• Monitor the patient for any side effects, particularly central nervous system effects such as dizziness, confusion, or insomnia.
• Educate the patient and their family on the importance of taking the medication as prescribed, especially within the first 48 hours of symptom onset.
• Assess for any history of renal impairment, as Amantadine dosage may need to be adjusted in patients with renal issues.
• Encourage fluid intake to help manage flu symptoms and facilitate the body's response to the medication.

✘Incorrect answer options:

Acyclovir (Zovirax) Acyclovir is an antiviral medication primarily used to treat infections caused by herpes viruses, such as herpes simplex and varicella-zoster. It is not effective against the influenza virus and would not be appropriate for treating respiratory flu.

Abacavir (Ziagen) Abacavir is an antiretroviral medication used in the treatment of HIV infection. It works by inhibiting the reverse transcriptase enzyme, which is crucial for HIV replication. It has no efficacy against the influenza virus, and thus, it would not be prescribed for a case of respiratory flu.

Ganciclovir (Cytovene) Ganciclovir is an antiviral medication used to treat cytomegalovirus (CMV) infections, especially in immunocompromised individuals. Similar to Acyclovir, Ganciclovir is not effective against the influenza virus, making it unsuitable for treating respiratory flu.

EXPLANATION

✔Correct answer:

Lactic acidosis. The most severe potential adverse effect of anti-hepatitis B agents, particularly nucleoside analogs like tenofovir and entecavir, is lactic acidosis. Lactic acidosis is a rare but life-threatening condition characterized by the buildup of lactic acid in the body, leading to a decrease in blood pH. This can occur because these medications can affect mitochondrial function, leading to impaired oxidative phosphorylation and a subsequent accumulation of lactic acid.

Lactic acidosis occurs when the body's cells produce lactic acid faster than it can be metabolized. This condition can be caused by a variety of factors, but in the context of anti-hepatitis B therapy, the drugs may impair mitochondrial DNA polymerase, leading to mitochondrial dysfunction. This dysfunction can disrupt normal cellular respiration, causing anaerobic metabolism to take over, which produces excessive lactic acid as a byproduct. If not recognized and treated promptly, lactic acidosis can lead to multi-organ failure and death.

Imagine your cells are like factories that need energy to operate, and they usually get it from oxygen (like clean energy). When something goes wrong with their power system (mitochondrial dysfunction), they switch to a backup generator that burns fuel inefficiently (anaerobic metabolism), producing harmful exhaust fumes (lactic acid). Too much of this can overwhelm the body, leading to severe consequences.

When starting a patient on anti-hepatitis B therapy, it's crucial for nurses to educate them on the symptoms of lactic acidosis, which can include unexplained fatigue, weakness, abdominal pain, shortness of breath, and muscle pain. Nurses should also ensure regular monitoring of the patient's blood lactate levels, liver function, and renal function.

• Educate the patient to report symptoms such as severe fatigue, muscle pain, or difficulty breathing immediately.
• Monitor liver and renal function tests, as these can provide early indicators of mitochondrial toxicity.
• Regularly assess the patient’s acid-base balance and lactate levels, especially if symptoms suggest lactic acidosis.
• Collaborate with the healthcare team to consider dose adjustment or discontinuation of therapy if signs of lactic acidosis emerge.

✘Incorrect answer options:

Bone marrow suppression. Bone marrow suppression is a severe adverse effect associated with some antiviral agents, particularly those used in HIV treatment (e.g., zidovudine), but it is not the primary concern with anti-hepatitis B agents.

Steatosis. Steatosis, or fatty liver, can be associated with long-term use of some antiviral medications, particularly those affecting mitochondrial function. However, it is not typically the most acute or severe concern compared to lactic acidosis.

Severe skin reactions. Severe skin reactions, such as Stevens-Johnson syndrome or toxic epidermal necrolysis, can occur with certain antiviral medications, but they are not the most common or severe adverse effect associated with anti-hepatitis B agents.

EXPLANATION

✔Correct answer:

Saquinavir. Saquinavir is the protease inhibitor that is considered safe for use during pregnancy and is not teratogenic. Teratogenicity refers to the capability of a substance to cause birth defects during fetal development. Among protease inhibitors, saquinavir has been studied more extensively and is generally regarded as safe to use in pregnant women with HIV to prevent maternal-fetal transmission of the virus.

Protease inhibitors are a class of antiretroviral drugs used in the management of HIV infection. They work by inhibiting the protease enzyme, which is crucial for the maturation of the virus. In pregnant women, controlling HIV viral load is essential to reduce the risk of transmitting the virus to the fetus. While some protease inhibitors carry risks of teratogenic effects, saquinavir is preferred because it does not exhibit these effects and is effective in maintaining viral suppression during pregnancy.

Think of saquinavir as a carefully designed tool that can effectively lock a door (protease enzyme) to prevent a problem (HIV replication) without damaging the surrounding structure (fetal development).

When caring for pregnant patients on antiretroviral therapy, nurses should monitor both maternal and fetal health closely, ensuring that the chosen medication regimen effectively controls the HIV infection while minimizing any potential risks to the developing fetus.

• Monitor viral load and CD4 counts regularly to ensure effective suppression of the virus during pregnancy.
• Educate the patient on the importance of medication adherence to prevent viral resistance and reduce the risk of mother-to-child transmission.
• Collaborate with obstetricians to provide comprehensive prenatal care, including regular fetal monitoring.

✘Incorrect answer options:

Darunavir. Darunavir is another protease inhibitor used in HIV treatment, but it is generally avoided during pregnancy because of potential teratogenic effects, particularly in the first trimester.

Indinavir. Indinavir is a protease inhibitor that has also been associated with potential risks during pregnancy, including teratogenicity and other adverse effects such as nephrolithiasis (kidney stones), making it less favorable for use in pregnant women.

Fosamprenavir. Fosamprenavir is metabolized to amprenavir, another protease inhibitor that is not recommended during pregnancy due to potential teratogenic effects and concerns about fetal safety.

EXPLANATION

✔Correct answer:

It deprives viruses of the necessary substances required to form DNA chains. Acyclovir is an antiviral medication primarily used to treat infections caused by herpes viruses, including herpes simplex virus (HSV) and varicella-zoster virus (VZV). The correct mechanism of action for acyclovir is that it mimics the structure of the nucleoside guanosine and gets incorporated into the viral DNA during replication. Once incorporated, acyclovir acts as a chain terminator, meaning that it prevents the addition of further nucleotides, thereby halting the elongation of the viral DNA chain. This disruption prevents the virus from replicating and spreading within the host.

Viruses, unlike bacteria, cannot replicate on their own and must hijack the host's cellular machinery to reproduce. By interfering with viral DNA synthesis, acyclovir effectively limits the replication and proliferation of the virus within the infected cells, helping to control the spread and reduce the severity of the infection.

Imagine a zipper (representing viral DNA) that is being zipped up. Acyclovir is like a broken zipper tooth—once it is inserted, the zipper can no longer close properly, stopping the virus from fully assembling its DNA and continuing its replication process.

When administering acyclovir, nurses should ensure that patients are well-hydrated, as the drug can crystallize in the kidneys, potentially leading to nephrotoxicity. It's also essential to educate patients on the importance of taking the medication as prescribed and completing the full course, even if symptoms improve early.

• Monitor renal function, especially in patients with preexisting renal conditions.
• Encourage patients to maintain adequate hydration during the course of treatment.
• Educate the patient on recognizing early signs of renal impairment, such as reduced urine output or back pain.

✘Incorrect answer options:

The exact mechanism is unknown, but it is thought to disrupt the protein coat of the virus. This option is incorrect because the mechanism of acyclovir is well understood. It does not disrupt the viral protein coat but rather interferes with DNA synthesis by acting as a chain terminator.

It competes with viral receptors present in host cells. This answer is incorrect because acyclovir does not function by competing with viral receptors. Medications like maraviroc, used in HIV treatment, work by blocking viral receptors on host cells, but this is not the mechanism of acyclovir.

It traps and directly disintegrates the viruses. This option is incorrect as well. Acyclovir does not trap or directly disintegrate viruses. Instead, it interrupts the virus's ability to replicate its DNA, effectively preventing the virus from multiplying.

EXPLANATION

✔Correct answer:

Foscarnet. Nurse Rachel should question the prescription of   foscarnet   for a patient with severe hypokalemia. Foscarnet is an antiviral medication used primarily to treat cytomegalovirus (CMV) infections, especially in immunocompromised patients, and acyclovir-resistant herpes infections. One of the significant adverse effects of foscarnet is that it can cause electrolyte imbalances, including hypokalemia (low potassium levels). Given that the patient is already experiencing severe hypokalemia, administering foscarnet could exacerbate this condition, leading to potentially life-threatening complications such as cardiac arrhythmias.

Potassium is a crucial electrolyte involved in maintaining the electrical activity of cells, particularly in cardiac muscle cells. Severe hypokalemia can disrupt normal heart function, leading to arrhythmias or even cardiac arrest. Foscarnet's ability to further lower potassium levels makes it a risky choice in patients who are already hypokalemic.

Think of potassium in the body like fuel for a car engine (the heart). If the fuel level is already low (hypokalemia), adding a substance that further reduces the fuel (foscarnet) could cause the engine to sputter or stop (cardiac arrhythmia).

For patients with hypokalemia, it's crucial to monitor electrolyte levels closely before and during the administration of medications that can affect potassium balance. Nurse Rachel should question the use of foscarnet in this patient and consult with the healthcare provider about alternative antiviral treatments or strategies to correct the hypokalemia before continuing treatment.

• Ensure frequent monitoring of electrolyte levels, particularly potassium, in patients receiving foscarnet.
• Consider preemptive potassium supplementation or correction of hypokalemia before initiating foscarnet therapy if it's deemed necessary.
• Monitor cardiac function closely due to the increased risk of arrhythmias associated with hypokalemia.

✘Incorrect answer options:

Cidofovir Cidofovir is an antiviral medication also used to treat CMV infections, particularly in patients with AIDS. While cidofovir can cause nephrotoxicity and requires monitoring of renal function, it is not specifically known to exacerbate hypokalemia.

Valganciclovir Valganciclovir is another antiviral agent used to treat CMV infections. Although it can cause neutropenia and anemia, it does not have a direct impact on potassium levels and would not be as concerning in a patient with hypokalemia.

Nevirapine Nevirapine is a non-nucleoside reverse transcriptase inhibitor (NNRTI) used in the treatment of HIV. It is not associated with causing hypokalemia, and thus, it would not be immediately concerning in the context of a patient with severe hypokalemia.